Disc drive having a printed circuit board port connector

ABSTRACT

The present invention is directed to a disk drive that includes a head disk assembly on a base plate, a cover sealably attached to the base plate to enclose the head disk assembly, and a printed circuit board fastened beneath the head disk assembly. The printed circuit board has a port connector at one end of the board opposite an end having power and signal connectors.

This Application is a divisional application of Ser. No. 09/285,936,filed Apr. 2, 1999, now U.S. Pat. No. 6,429,999, which is a continuationof application of Ser. No. 08/622,925, filed Mar. 27, 1996, now U.S.Pat. No. 5,956,213, which is a continuation application of Ser. No.08/400,463, filed Mar. 7, 1995, now abandoned, which is a continuationapplication of Ser. No. 08/110,539, filed Aug. 23, 1993, now abandoned,which is a divisional application of Ser. No. 07/796,576, filed Nov. 22,1991, now abandoned, which is a continuation-in-part of co-pendingapplication Ser. No. 07/549,283, filed Jul. 6, 1990 now abandoned, whichis a continuation-in-part of co-pending application Ser. No.0/7/147,804, filed Jan. 25, 1988, now U.S. Pat. No. 4,965,684.

CROSS-REFERENCE TO RELATED APPLICATIONS

1) LOW HEIGHT DISK DRIVE, inventor Frederick M. Stefansky, Ser. No.07/147,804, Filed Jan. 25, 1988, now U.S. Pat. No. 4,965,684;

2) DISK DRIVE SYSTEM CONTROLLER ARCHITECTURE, inventors John P. Squires,Tom A. Fiers, and Louis J. Shrinkle, Ser. No. 057,289, filed Jun. 2,1987, now U.S. Pat. No. 4,979,056;

3) DISK DRIVE SOFTWARE SYSTEM ARCHITECTURE, inventors John P. Squires,Tom A. Fiers; and Louis J. Shrinkle, Ser. No. 488,386, filed Feb. 23,1990, now U.S. Pat. No. 6,279,108, which is a continuation of Ser. No.057,806, filed Jun. 2, 1987, now abandoned;

4) DISK DRIVE SYSTEM CONTROL ARCHITECTURE UTILIZING EMBEDDED REAL-TIMEDIAGNOSTIC MONITOR, inventor John P. Squires, Ser. No. 423,719, filedOct. 18, 1989, now U.S. Pat. No. 4,979,055, which is a continuation ofSer. No. 058,289, filed Jun. 2, 1987, now abandoned;

5) LOW-POWER HARD DISK DRIVE ARCHITECTURE, inventors John P. Squires andLouis J. Shrinkle, filed Aug. 7, 1990, Ser. No. 564,693, now U.S. Pat.No. 5,402,200, which is a continuation of Ser. No. 152,069, filed Feb.4, 1988, now abandoned;

6) DISK DRIVE SYSTEM USING MULTIPLE EMBEDDED QUADRATURE SERVO FIELDS,inventors Louis J. Shrinkle and John P. Squires, Ser. No. 386,504, filedJul. 27, 1989, now U.S. Pat. No. 5,381,281;

7) MAGNETIC PARKING DEVICE FOR-DISK DRIVE, inventor, Frederick MarkStenfansky, Ser. No. 643,703, filed Jan. 22, 1991, now U.S. Pat. No.5,170,300, which is a continuation of Ser. No. 269,873, filed Nov. 10,1988, now abandoned;

8) MULTIPLE MICRO CONTROLLER HARD DISK DRIVE CONTROL ARCHITECTURE,inventors John P. Squires, Charles M. Sander, Stanton M. Keeler, andDonald W. Clay, Ser. No. 07/611,141, filed Nov. 9, 1990, now U.S. Pat.No. 5,261,058.

Each of these related Applications is assigned to the assignee of thesubject Application and hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to disk drives; more particularly to hard(or fixed) disk prompted reductions in the size and increases in memorycapacity of disk drives.

2. Description of the Related Art.

Developments in personal computers, portable computers and lap topcomputers have prompted reductions in the size and increases in memorycapacity of disk drives. Attempts to provide further reductions in thesize and weight, and increases in durability and memory capacity ofexisting disk drives have been met with limited success. The size(particularly the height) and weight of fixed or hard disk drives andthe inability of existing hard disk drives to withstand physical shocksand/or vibrations have been factors which have prevented theincorporation of fixed disks in lap-top and in some cases even largerportable computers.

Existing disk drives incorporate a large number of mechanical parts.Each part in a disk drive also represents an increase in the weight ofthe drive and the space occupied by the drive. A large number ofmechanical components makes manufacturing difficult and expensive andincreases the possibility and probability of the mechanical failure ofthe drive. Importantly, the number of mechanical components is relatedto the ability of the drive to survive physical shocks and vibrations.

Resistance to physical shocks and vibrations is critical to protectingthe disk or disks, the head or heads, and the various bearings in a diskdrive from damage; in particular, it is necessary to prevent damage tothe disks which can cause a loss of data, and damage to the heads or thebearings which can end the life of a drive, resulting in a total loss ofdata. Prior disk drives, however, have limited resistance to physicalshocks. Resistance to physical shocks is of paramount importance inportable computers.

In conventional drives mechanical distortion or flexing of themechanical components of a disk drive which support the heads and diskscauses tracking problems by moving the heads, which are mounted at onepoint on the supporting components, relative to the disk, which ismounted at another point on the supporting components. The headsassociated with the top and bottom surface of a disk can move relativeto the disk to the point where the different heads are in differentcylinders—a cylinder being defined as a vertical segment representingthe same track on the top and bottom surface of the disk. This problemis known as mechanical off-track and is compounded by increased trackdensities.

Another problem with prior disk drives is the difficulty in sealing thedrives to protect the disks from contaminants. This difficulty arises inpart, from the large number of points at which access is provided to theenvironment in which the disk resides. These access points are utilizedto bring to the interior of the disk drive electrical circuits whichprovide current to the motor which rotates the disk, transmit datasignals to and from heads which read and record information on thedisks, and in some instances, provide current to a voice coil forpositioning the head (or heads) which respect to the disk or disks.

Many of these disadvantages of prior disk drivers are attributable tothe casing—a three-dimensional casting or so-called “toilet bowl”—inwhich the disks reside. Such a casing is a large, three dimensionalpiece of cast metal, usually aluminum, having a round portion where thedisks reside—hence the name “toilet bowl.” A top plate covers the entireopen top of the casing, forming a seal therewith.

The spindle on which the disks rotate is supported by and extendsthrough both the casing and the cover.

The protrusion of the spindle through the casing and the cover providespoints of entry for contaminates. Further, in disk drives using steppermotors to position the heads with respect to the disk, the stepper motoris located outside of the casing, requiring a seal between the steppermotor and the casing. Acknowledging the existence of points wherecontaminants can enter the disk drive, manufacturers of conventionaldisk drives provide a breather filter and design the disk drives so thatthe rotation of the disks causes the disk drivers to exhaust air throughleaks in the seals and to intake air only through the breather filter.However, a fairly course filter must be provided in the breather filterfor flow of the air to exist, and thus contaminants enter the disk drivethrough the filter paper.

A cast casing is difficult to manufacture with precision, particularlythe location of mounting points for elements of the drive supported bythe casing. Mounting holes must be drilled after the casting is cast,and the mounting holes must be aligned with the casing and with eachother. More importantly, however, a three-dimensional, cast casingflexes due to thermal stresses causing the above-mentioned mechanicaloff-track problems.

In conventional disk drives which use a voice coil to pivot an actuatorarm in order to position the heads with respect to the disk, a flexcircuit, having one end attached to the actuator arm and the other endattached to a fixed point in the disk drive, transfers the informationsignals to and from the heads. The standard orientation of such a flexcircuit is a loop extending away from the disk. The distance between thepoint at which the flex circuit is attached to the actuator and the endof the disk drive is limited, and thus the radius of the arc or curve ofthe flex circuit is small and the length of the flex circuit itself islimited. Therefore, the entire flex circuit moves when the actuator armis pivoted and a torque is exerted on the actuator arm by the flexcircuit. The torque exerted on the actuator arm must be compensated for,either added to or subtracted from the torque created by the voice coilwhen performing a seek operation. This compensation is complicated bythe fact that the torque exerted on the actuator by the flex circuitvaries with the position of the actuator.

Various types of locking (or latch) devices have been used to lock thearm of a voice coil in a particular position when the disk drive is notoperating. The trend in latch devices is to utilize a high power unitwhich is separately assembled to provide reliability. However, highpower latch devices generate a large amount of heat which is notdesirable in a disk drive or any other area in a computer. Further, theoperation of conventional latch devices can be position dependent. Thus,the orientation of the dick drive and the computer in which the diskdrive is installed could affect the reliability of the latch device.Such a positional dependence of reliability is not satisfactory forportable computers.

With the ever-increasing storage available on individual magnetic disks,and the ever-increasing speed at which microprocessors such as Intel's80386 and 80486 chips operate, the data access time of the disk drive iscritical to overall system performance. In many cases, the speed atwhich the disk accesses data and provides it to the microprocessor isthe main performance bottleneck in the system. One critical factor indisk access time is the “seek time” of a drive, generally defined as thetime the actuator takes to access particular data at a particular tracklocation on the magnetic disk. The total access time is generally afunction of the efficiency of the actuator motor in moving theread/write heads along the arcuate path between consecutive tracks ofthe disk, and the data throughput of the control electronics.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a diskdrive having a printed circuit board fastened beneath the base platesupporting the head disk assembly. This printed circuit board has powerand signal connectors disposed at one end of the printed circuit boardand another connector positioned at an opposite end of the printedcircuit board. This port connector may be positioned toward an openingin an end wall of the base plate and may, for example, be utilized toprovide a test connection to the drive for test purposes.

These and other objects of the present invention are provided by a diskdrive including a base plate supporting a head disc assembly, a coverover the head disc assembly fastened to the base plate to provide acontrolled environment for the head disc assembly between the base plateand cover, and a printed circuit board adjacent to an underside of thebase plate. The base plate preferably has parallel longitudinal sidewalls and end walls forming a space under the base plate for receivingcomponents mounted on the printed circuit board, wherein one of the endwalls has an opening therethrough facing a power connector and a signalconnector on the printed circuit board and the other of the end wallshas an opening therethrough aligned with another connector on theprinted circuit board facing outward in a parallel and oppositedirection to the power and signal connectors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-7 illustrate a first embodiment of the disk drive of the presentinvention. In particular:

FIG. 1 is an isometric view of the first embodiment of a disk driveaccording to the present invention;

FIG. 2 is an isometric view of the first embodiment of the disk drive ofthe present invention with the cover removed;

FIG. 3 is a cross-sectional view along line 3-3′ of FIG. 2;

FIG. 4 is an exploded view of the first embodiment of the disk drive ofthe present invention;

FIG. 5 is an end view of the first embodiment of the disk drive of thepresent invention;

FIG. 6 illustrates the actuator assembly; and

FIG. 7 illustrates the latch mechanism.

FIGS. 8-12 illustrates a second embodiment of the disk drive of thepresent invention. In particular:

FIGS. 8 is an isometric view of the second embodiment of a disk driveaccording to the present invention with the cover removed;

FIGS. 9 is an expanded isometric view of the second embodiment of thedisk drive of the present invention;

FIGS. 10 is an exploded, isometric, bottom view of the printed circuitboard and the base of the second embodiment of a disk drive according tothe present invention;

FIGS. 11 is an end view of the second embodiment of a disk driveaccording to the present invention;

FIGS. 12 is an exploded, isometric view of a portion of the actuator andthe latch mechanism utilized in the second embodiment of the presentinvention.

FIGS. 13-19 illustrate a third embodiment of the disk drive of thepresent invention. In particular:

FIG. 13 is an exploded, isometric view of the third embodiment of thedisk drive according to the present invention;

FIG. 14 is a plan view of the third embodiment of the disk driveaccording to the present invention;

FIG. 15 is a view along line 15—15 in FIG. 14;

FIG. 16 is an exploded, partial view of the actuator assembly of thethird embodiment of the disk drive of the present invention;

FIG. 17 is a partial plan view of the actuator assembly of the thirdembodiment of the present invention;

FIG. 18 is a cross-sectional view along line 18—18 in FIG. 17;

FIG. 19 is an enlarged, cross-sectional view of the gasket and coverassembly along line 19—19 in FIG. 13.

FIG. 20 is a plan view of the actuator assembly of the third embodimentof the present invention with the top plate and top magnet removed,detailing the relationship between the actuator coil and actuator magnetconstruction used therein.

FIG. 21 is a graph representing the relative magnitude of the torqueexerted on an actuator arm by the voice coil motor of the firstembodiment of the disk drive of the present invention over the fullstroke of the actuator movement from the inner diameter to the outerdiameter of the disk.

FIGS. 22-23 are graphs representing the relative magnitude of the torqueexerted on an actuator arm by the voice coil motor of the secondembodiment of the disk drive of the present invention over the fullstroke of the actuator's movement.

FIG. 24 is a graph representing the relative magnitude of the torqueexerted on an actuator arm by the voice coil motor of the thirdembodiment of the disk drive-of the present invention over the fullstroke of the actuator's movement.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Disk drives according to the present invention will be described withreference to FIGS. 1-24. The disk drives described herein include, forexample, one or two hard disks with a magnetic coating and utilizeWinchester technology; however, the disk drive of the present inventionmay utilize various numbers of disks and other types of disks, forexample, optical disks, and other read/write technologies, for example,lasers. The diameter of the disks utilized in the disk drive of thepresent invention have a diameter on the order of 3.75 inches, orso-called “3½” disks; the disk drive of the present invention can beimplemented with disks of other diameters whether larger or smaller than3.75 inches.

A disk drive in accordance with either the first, second, or thirdembodiments of the present invention has the following outlinedimensions: Height 1.0″ (2.54 cm); Length 5.75″ (14.61 cm); and Width4.0″ (10.16 cm). The total weight is slightly over one (1) pound; forthe first embodiment, 1.3 lbs (0.59 kg) for the second embodiment, and1.16 lbs for the third embodiment. Thus, the disk drive of the presentinvention is one-half (½) of the size of a one-half (½) height 5¼″ inchdisk drive. Importantly, the disk drive of the present invention weightapproximately {fraction (1/3 )} to ½ of the weight of standard 3½″ diskdrives of 20 Mb capacity. Even greater proportional reductions areprovided when the first embodiment is formatted for 40 Mb capacity, andthe second embodiment is formatted for 120 Mb capacity, and the thirdembodiment is formatted with a storage capacity of approximately 213 Mb,without any change in size or weight.

Although not to scale, FIGS. 1, 14, and 15 illustrate the relationshipbetween the length, width, and height of the disk drive; and thus lowprofile of the disk drive. In particular, the height “h” of the diskdrive of the present invention is one inch (1″)

First Embodiment and Common Features

One feature of the first embodiment which provides the low height of thedrive is the sloped profile of base plate 12 and cover 14. The slopedprofile provides extra vertical space below base plate 12 at the firstend 10 a of the disk drive and provides extra vertical space betweenbase plate 12 and cover 14 at the second end 10 b of the disk drive 10.If the sloped profile were not provided, the amount of space allocatedabove and below base plate 12 would be the maximum amount of spaceprovided at the respective first and second ends 10 a, 10 b of the diskdrive 10; accordingly, the overall height of the disk drive would beincreased. The cover 14 is sealably attached to base plate 12 to providea controlled environment between base plate 12 and cover 14. A gasket 16(FIG. 4) between base plate 12 and cover 14 provides the seal. Theability to provide a controlled environment alleviates the need for abreather filter and allows the disk drive of the present invention touse an internal air filtration system. The seal provided by gasket 16 isstable, during operation of the disk drive, at pressures experienced ataltitudes from 200 feet below sea level to 10,000 feet above sea level.

As Shown in FIG. 2 the internal components of the disk drive areseparated into three interrelated groups: disk 20 and spin motor 22,actuator assembly 24 for positioning heads 26 with respect to disk 20,and header assembly 28 including header 30, bracket 32, reverse flexcircuit 34 and coil 36 for pivoting latch arm 38.

Actuator assembly 24 includes pivotal actuator arm 40, heads 26 (FIG. 4)mounted at a first end of actuator arm 40, an actuator coil 42 mountedat a second end of actuator arm 40 on the opposite side of the pivotpoint from the first end of the actuator arm, and a magnet structure 44.Magnet structure 44 supports magnets 46 (FIG. 4) and its components, asdescribed in detail below, are formed of magnetically permeable materialto provide returns for the magnetic field generated by magnets 46. Themagnet structure 44 and actuator coil 42 are arranged so that a currentin coil 42 passes through the magnetic fields created by magnets 46 tocreate a force which pivots actuator arm 40. Currents passing inopposite directions of coil 42 create torques in opposite directions andpivot actuator arm 40 to position heads 26 at all locations between andincluding inside and outside diameters 48 and 50 of disk 20.

In a conventional disk drive utilizing a voice coil, a flex circuit isprovided to the region between header 30 and actuator arm 40. Reverseflex circuit 34 curves toward the disk, thereby allowing latch coil tobe placed between header 30 and actuator arm 40.

A printed circuit assembly (or control means) 52 is attached to thebottom of base plate 12. Header 30 carries all of the electrical signalsfrom the printed circuit assembly 52 to the controlled environmentbetween base plate 12 and cover 14. Header 30 has a minimum number ofpins due to the fact that a DC motor requiring only three (3) leads isutilized. Such a motor is described in U.S. Pat. No. 4,876,491, entitledMETHOD AND APPARATUS FOR BRUSHLESS DC MOTOR SPEED CONTROL, filed Jul. 1,1986, inventors John P. Squires and Louis J. Shrinkle, assigned to theAssignee of the subject application.

The structure of the disk drive 10 of the present invention, whichprovides the disk drive with a low overall height, will be describedwith reference to FIG. 3, which is a cross-sectional view along line3—3′ in FIG. 4. As shown in FIG. 5, base plate 12 includes two rails 54a and 54 b at first and second sides 12 a and 12 b of base plate 12.Rails 54 a are constructed so that the mounting surface 12 e of the baseplate 12 sits at an angle with respect to the plane of the surface onwhich rails 54 a and 54 b rest. This angled relationship of base plate12 and the support surface provides more room below base plate 12 at thefirst end 12 a of the base plate than at the second end 12 b of the baseplate. Only a small amount of space is necessary for printed circuitassembly 52, including the components mounted thereon; however, it isnecessary to provide a connector 56 and a power plug on printed circuitassembly at the first end 12 a of base plate 12 (FIG. 1), both of whichrequire more vertical space than the printed circuit assembly 52. Theslope of base plate 12 provides the necessary vertical space forconnector 56 and power plug 58 beneath the first end of the base plate12 a. Connector 56 provides an interface between the printed circuitassembly 52 and a host computer (not shown) and power plug 58 providesan interface between printed circuit assembly 52 and an external powersource (not shown).

Conversely, disk 20 is the only component located above the first end ofthe base plate 12 a, whereas the actuator assembly 24 is located abovethe second end of the base plate 12 b. Actuator assembly 24 requiresmore vertical space than disk 20 and the slope of base plate 12 providesmore space above the second end of the base plate 12 b than above thefirst end of the base plate 12 a in order to accommodate the actuatorassembly 24. As shown in FIG. 1 the portion of cover 14 which meets withbase plate 12 has an angle which corresponds to the angle of the baseplate, and thus the top of the cover 14 is parallel with the supportsurface. Therefore, even though the base plate is sloped, the profile ofthe disk drive 10 is a rectangle as opposed to a parallelogram.

Disk 20 lies in a plane which is parallel to the support surface andwhich forms an angle with the plane of base plate 12. All of the supportpoints on the mounting surface 12 e (FIG. 5) of 1-5 base plate 12 aredesigned so that the internal components (e.g., actuator assembly 24)lie in plane parallel to the plane of disk 20 and the plane defined bysupport points 55 of rails 54 a, 54 b.

The structure and operation of actuator assembly 24 will be explainedwith reference to FIGS. 4-7. The function of the actuator assembly 24 isto position heads 26 with respect to the surfaces of disks 20 bypivoting actuator arm assembly 40. More specifically, to position theheads 26 over individual tracks on disk 20. Heads 26 are supported onactuator arm 40 by flexures 60. A bearing cartridge 62, which is fixedto the base plate 12, is inserted in actuator arm 40 to provide a pivotpoint. Actuator arm 40 is attached to bearing cartridge 62 by a clipring 63. Using clip ring 63 instead of epoxy allows the bearingcartridge 62 to be tested prior to assembly and cleaned independently ofthe actuator arm 40. Actuator coil 42 is provided on actuator arm 40 onthe opposite side of the pivot point from heads 26. Actuator arm 40,including all of the components attached thereto, is precisely balanced,i.e., equal amounts of weight are provided on either side of the pivotpoint so that the positioning of heads 26 is less susceptible to linearshock and vibration.

The force utilized to pivot arm assembly 40 is provided by a voice coilassembly. The voice coil assembly includes actuator coil 42 and magnetstructure 44. Magnet structure 44 comprises top and bottom plates 64, 66formed of magnetically permeable material, support posts 68, 70 alsoformed of magnetically permeable material, and first and second magnets46 a, b attached to the top plate 64. Top and bottom plates 64, 66 inconjunction with support posts 68, 70 function as returns for themagnetic fields provided by first and second magnets 46 a, b. It isimportant that there are no air gaps between support posts 68, 70 andeither the top or bottom plate 64, 66; any air gap would create adiscontinuity in the return, greatly reducing the strength of themagnetic field.

First and second magnets 46 a, b have opposite poles attached to topplate 64 (i.e., the south pole of first magnet 46 a and the north poleof magnet 46 b are attached to the top plate 64) to provide first andsecond magnetic fields B₁, B₂ between respective ones of the first andsecond magnets 46 a, b and bottom plate 66. First and second magneticfields B₁, B₂ are encompassed in three closed magnetic field loops. Thefirst closed magnetic field loop extends between the first magnet 46 aand bottom plate 66 and passes through a return provided by bottom plate66, first support 68, and top plate 64. The second closed magnetic looppasses from first magnet 46 a to bottom plate 66, through bottom plate66 and between bottom plate 66 and second magnet 46 b, and from secondmagnet 46 b to first magnet 46 a via top plate 64. The third closedmagnetic loop extends between bottom plate 66 and second magnet 46 b andpasses through a return provided by top plate 64, second support 70, andbottom plate 66. By containing the magnetic fields B₁, and B₂, inreturns, the magnetic field intensity of each field is increased in theregion between the respective first and second magnets 46 a, b andbottom plate 66; the strength of the magnetic field in this region isdirectly related to the torque which the voice coil exerts on theactuator arm 40, and thus the rotational velocity of actuator 40 and theseek times for the drive.

Actuator coil 42 is positioned so that it carries a current in oppositedirections in first and second magnetic fields B₁, and B₂.

The force on a current carrying wire in a magnetic field is proportionalto the magnetic field intensity, and is expressed by the equationF=idl×B, where F is the force, i is the current, l is the length of thewire, and B is the magnetic field. Passing a current in oppositedirections in actuator coil 42 provides respective forces F, and F₂(FIG. 2); these forces F, and F₂ pivot actuator arm 40 in oppositedirections.

Crash stops are provided to limit the pivoting movement of actuator arm40 so that heads 26 travel only between selected inside and outsidediameters 48, 50 of disk 20. An outside diameter crash stop is providedby a sleeve 76 (FIG. 5) fitted on support post 68. When the pivotingmotion of actuator arm 40 places heads 26 at the outside diameter 50 ofdisk 20 a portion of the actuator arm 40 contacts outside diameter crashstop 76, thereby preventing further movement of the heads 26. An insidediameter crash stop is provided by the portion of the latch mechanism(FIG. 7) and is described below.

Reverse flex circuit 34 for carrying electrical signals from header 30to heads 26 and actuator arm assembly 24 will be described withreference to FIGS. 2, 4, 6 and 7. The reverse flex circuit is separatedinto three portions. A first portion 80 carries current to actuator coil42. A second portion 82 is a ground plane which separates the currentcarrying portion 80 from a third data-carrying portion 84. The datacarrying portion 84 provides signals to heads 26 for recordinginformation on disk 20 and carries signals from the heads 26 to theprinted circuit assembly 52, via header 80, when reading data from disk20. Interference with the relatively week data signals which wouldotherwise be caused by the larger currents necessary for actuator coil42 passing through the first portion 80 of the reverse flex circuit 34is prevented by the provision of ground plane 82.

The reverse flex circuit 34 is electrically connected to pins 31 a ofheader 30; however, pins 31 a also serve to position the reverse flexcircuit 34. In particular, bracket 52 supports reverse flex circuit 34and latch coil 36. Bracket 32 is attached to base plate 12 by a singleattachment point 86 and is rotationally positioned by the engagement ofreverse flex circuit 34 and pins 31 a—the positioning of latch coil 36being important to the operation of the latch mechanism as describedbelow. A stiffener 88 is attached to reverse flex circuit 34 in the areawhere it engages pins 31 a and is attached to bracket 32 to provide therigidity necessary to rotationally position bracket 32, and tofacilitate engagement of reverse flex circuit 34 and pins 31 a. Reverseflex circuit 34 is parallel to the plane of base plane 12 in the regionof header 31 but passes through a bend of approximately 90 degrees sothat it forms the loop which extends towards disk 20 and connects header30 to actuator assembly 24.

First portion 80 of reverse flex circuit 34 terminates at the pointwhere reverse flex circuit 34 joins actuator arm 40; however, the secondand third portions 82 and 84 wrap around a shoulder 90 of actuator arm40 which surrounds bearing cartridge 62. Wrapping the second and thethird portions 82 and 84 of reverse flex circuit 34 around shoulder 90provides access to current-carrying wires are provided on the side ofthe flex circuit which faces the base plate in the region where reverseflex circuit 34 engages pins 31 a of header 30, and thus on the insideof the curved portion of reverse flex circuit 34 extending from bracket32 to actuator arm 40. As the first and second portions 82 and 84 wraparound shoulder 90, the side of reverse flex circuit 34 on which thecurrent-carrying wires are provided is exposed at the end of reverseflex circuit 34, facilitating the attachment of wires 91 which connectheads 26 to reverse flex circuit 34. If wires 91 were to be connected toreverse flex circuit 34 at the point where reverse flex circuit 34 firstcontacts actuator arm 40, it would be necessary to wrap wires 90 aroundreverse flex circuit 34 or to provide connections through the reverseflex circuit 34—both being more complex and less desirable manners ofproviding electrical connections between wires 91 and reverse flexcircuit 34. Any torque exerted on actuator arm 40 by any means otherthan the voice coil assembly affects the function of actuator assembly24 in positioning heads 26 with respect to disk 20, particularly thetrack following any seek functions described in the above referencedpatents entitled DISK DRIVE SOFTWARE SYSTEM ARCHITECTURE and DISK DRIVESOFTWARE SYSTEM ARCHITECTURE UTILITIES IMBEDDED REAL TIME DIAGNOSTICMONITOR. The force provided by the voice coil assembly must becontrolled to compensate for the force exerted by the reverse flexcircuit 34. Accordingly, the radius R (FIG. 7) of the curve in reverseflex circuit is made as large as possible to minimize the torque exertedon actuator arm 40 by reverse flex circuit 34. Indeed, the radius of thecurve in reverse flex circuit 34 is approximately twice as large as theradius in the curve of a conventional flex circuit. In addition, thereverse flex circuit 34 moves in an essentially linear manner whenactuator arm 40 rotates, whereas a conventional reverse flex circuitmust bend throughout its curve. Accordingly, the torque exerted onactuator arm 40 by reverse flex circuit is greatly reduced with respectto the torque exerted by a conventional flex circuit.

Another advantage provided by reverse flex circuit 34 is the ability toplace latch coil 36 in a position where a conventional flex circuitwould be located, and thus to integrate latch coil 36 with reverse flexcircuit 34 and bracket 32. Separate wires from header 30 to latch coil36 are not necessary. Further, installing integrated group of componentsrequires fewer steps than installing individual components. In addition,the critical positioning of latch coil 36 is provided by reverse flexcircuit 34 and stiffener 88 controlling the pivotal position of bracket32, as described above.

All connections between the sealed environment between base plate 12 andcover 14 and printed circuit assembly 52 are provided by header 30. Pins31 a, which engage reverse flex circuit 34, also engage motor wireconnector 92. Pins 31 b extend below base plate 12 and engage a rearentry connector (not shown) on printed circuit assembly 52. A rear entryconnector is utilized because the integrated and discrete circuitcomponents and the surface wirings are on the side of printed circuitassembly 52 facing away from base plate 12.

A latch mechanism for locking the actuator arm 40 in an orientationwhere heads 26 are positioned at the inside diameter 48 of disk 20, willbe described with reference to FIGS. 4, 5 and 7. During power-down ofthe disk drive 10 control means 52 causes actuator assembly 24 to pivotthe actuator arm 40 to the position where the heads 26 are at the insidediameter of the disk over a non-data area of disk 20 before therotational speed of the disk is decreased to the point where the heads26 land on the disk 20. Thus, the heads 26 land only on the non-dataarea at the inside diameter of the disk 20.

The electromagnetic latch includes latch coil 36, a latch arm 38 whichpivots on pivot 94 and has a finger 96 for engaging latch notch 98 inactuator arm 40, and a spring 100 for biasing the latch arm 38 to thelocked position.

An electromagnet, including latch coil 36 and swivel plate 104, is usedto pivot latch arm 38 to the unlocked position against the force ofspring 100. Latch coil 36 includes a capture plate 106 having an outerwall 108 and a center pole 110. The outer wall 108 and center pole 110form opposite poles of an electromagnet, and when a current is passedthrough a coil (not shown) the magnetic field of capture plate 106attracts swivel plate 104; swivel plate 104 is mounted on the latch arm38 so that it can swivel in all directions and be flush with the outerwall 108 when the swivel plate 104 is captured by the electromagnet.Contact between the entire outer wall 108 and swivel plate 104 isnecessary to provide reliability in the capture and retention of theswivel plate 104. Center pole 110 of capture plate 106 is stepped sothat only a small contact area exists between center pole 110 and swivelplate 104; this small contact area causes the latch coil 36 to releasethe swivel plate 104 when the current in the coil (not shown) isdiscontinued. A high DC voltage is applied to the latch coil 36 for ashort time to capture the swivel plate 104. Then, the applied voltage isreduced to a small capture maintenance level. Thus, this structure islow in power consumption and heat dissipation. Further, despite the lowpower consumption of the latch coil 36 it is highly reliable in itscapture, holding, and release of swivel plate 104.

Spring 100 is a linear spring engaging finger 96. To reduce springtravel, thereby providing a constant and larger spring force, spring 100is terminated outside the pivot point of pivot 94.

Finger 96 also serves as the inside diameter crash stop. Finger 96 iswell suited for the inside diameter crash stop because it is positionedto engage notch 98 which is at one edge of opening 102 in actuator arm40. The abutment of finger 96 and the same edge of opening 102 when thelatch is unlatched provides the inside diameter crash stop. However, thepivoting movement of latch arm 27 in moving to the latched positionreduced the distance between pivot 94 and the edge of opening 102.Therefore, the actuator arm 40 pivots slightly to move the heads beyondthe inside diameter 48 to a non-data area.

The above-described structure of the disk drive of the present inventionprovides excellent protection from shock and vibration. In particular,the disk drive will withstand nonoperating shocks of 200 g's andoperating shocks, without nonrecoverable errors, of 5 g's. Nonoperatingvibration of 2 g's in the range of 5-500 Hz is the specified tolerablelimit. Operating vibration, without nonrecoverable data, is specified at0.5 g's for the range of 5-500 Hz.

The disk 20 has 752 tracks per surface due to the ability of theactuator assembly 24 to operate with a track density of 1150 tracks perinch. Thus, utilizing 26 blocks per track and 512 bytes per block, thedisk drive of the first embodiment has a formatted capacity of 20MBytes. The actuator assembly 24 provides an average seek time of 28 msand a track-to-track seek time of 7 ms. The average seek time isdetermined by dividing the total time required to seek between allpossible ordered pairs of track addresses by the total number of orderedpairs addressed.

The assembly of the disk drive 10 of the present invention requires lesssteps than assembly of conventional disk drives. The spin motor 22 anddisk 20 are attached to base plate 12. Then, an integrated actuatorgroup, including actuator arm 40, bracket 32, reverse flex circuit 34,and latch coil 36, all previously assembled, is installed. Magnetstructure 44 is then placed on one of its attachment points and pivotedinto position so that the portion of actuator arm 40 holding actuatorcoil 42 extends between the top and bottom plates 64, 66 of the magnetstructure 44. Latch arm 36 is then placed on its pivot point. The disk20 is then pack written, and thereafter cover 14 is attached. Finally,printed circuit assembly 52 is attached outside of the clean room.

Second Embodiment

A disk drive 200 in accordance with the second embodiment of the presentinvention will be described with reference to FIGS. 8-12.

As shown in FIGS. 8-10, the construction of disk drive 200 includes abase 212 and a cover 214. Gasket 216 provides a sealed, controlledenvironment between base 212 and cover 214. First and second disks 220,221 are supported on base 212 and rotated by spin motor 222. Motor 222is mounted in a well 223 in base 212, thereby allowing lower disk 221 tobe as close as possible to the top surface of base 212.

An actuator assembly 224 positions heads 226 a-d with respect to disks220 and 221; heads 226 a and 226 b read information from and writeinformation to respective, opposed surfaces of disk 220, and heads 226 cand 226 d read information from and write information to respective,opposed surfaces of disk 221. Tables 1 and 2 below specify certaincharacteristics of disks 220 and 221 and heads 226 a-d.

TABLE 1 Number of Disks 2 Number of Data Surfaces 4 Number of DataCylinders 1522 cylinders (Tracks per surface) Sectors per Track 40physical 39 accessible Bytes per Sector 662 Data Bytes per Sector 512bytes Data Capacity per Data 30 Mbytes Surface (formatted) Total DataCapacity (formatted) 120 Mbytes

TABLE 2 Disk Diameter 95 millimeters 3.74 inches Data Track Band Width20.32 millimeters 0.8 inches Track Density 1850 tracks/inch Bit Density(max) 23,800 fci

Controller 227, including printed circuit board 28 and circuitry 229mounted on circuit board 228, provides control signals to spin motor 222and actuator assembly 224, and provides data signals to and receivesdata signals from heads 226 a-d. Header 230 provides all electricalconnections between controller 227 and the environment between base 212and cover 214. Header 230 comprises conductive pins 231 embedded in aplastic header 232 which is then potted in base 212. A reverse entryconnector 237 mounted on the front side 228 a of printed circuit board228 receives pins 231; pins 231 pass through printed circuit board 228to enter connector 236. Bracket 232 supports a flex circuit 233,including a reverse flex circuit loop 234, and connector 236 whichprovides electrical interconnections between flex circuit 233 and pins231.

With reference to FIGS. 12, actuator assembly 224 includes pivotableactuator arm 240 and an actuator motor. The actuator motor is aso-called voice coil motor comprising coil 242 (provided on actuator arm240), first and second magnets 246 a, 246 b, top plate 264, bottom plate266, first support post 268, and second support post 270. Top and bottomplates 264 and 266, in conjunction with first and second support posts268, 270 create returns for the magnetic fields provided by first andsecond magnets 246 a and 246 b. The operation of the voice coil motor isdescribed above with respect to the first embodiment.

The structure which enables disk drives 200 of the second embodiment ofthe present invention to include 2 disks, 220 and 221, lying in parallelplanes within a one inch height form factor disk drive will be describedwith reference to FIGS. 8-10. In the first embodiment of the presentinvention the sloped profile of base 12 allowed the use of a fullyshrouded power connector 58. In particular, power connector 58 wasprovided at the first end 10 a of disk drive 10 where the sloped profileprovided more room underneath base 12 and less room between base 12 andthe top of cover 14. In the second embodiment, base 212 has first andsecond side rails 213 a and 213 b, and the mounting surface of base 212is parallel to the plane defined by support points 215 a-g. The spacebelow base 212 is the same at both ends of drive 200; in the secondembodiment a sloped profile is not utilized. In comparison with thefirst embodiment, the uniform height of rails 213 a and 213 b is thesame as the height to rails 54 a and 54 b at the second end 10 b ofdrive 10. Accordingly, the space between base 212 and cover 214 isincreased at the end of drive 200 where disks 220 and 221 reside. Thisincreased space between base 212 and cover 214, combined with theplacement of motor 222 in well 223, allows two disks 220 and 221 to beprovided in substantially parallel planes.

Printed circuit board 228 is mounted to base 212 by screws 254 a-c, andan insulating sheet 255 is provided between printed circuit board 117and base 212 to prevent short circuiting of the solder points appearingon the back side 228 b of printed circuit board 228 which faces base212. Printed circuit board 228 has an opening 253, and well 223protrudes through opening 253.

The reduced height of rails 213 a and 213 b at the end of drive 200where interface connector 256 and power connector 258 reside requiredfor the removal of part of the shrouding from power connector 258. Thus,pins 259 of electrical connector 258 are not protected by shroud 260 inthe region between pins 259 and base 212. However, because the connectorwhich attaches to pins 259 is itself insulated, there is no danger ofshorting pins 259 to base 212. A third connector 257, used for testpurposes, is provided at the opposite end of drive 200 from connectors256 and 258 as shown in FIGS. 11.

A latch mechanism for locking actuator arm 240 will be described withreference to FIGS. 11 and 12. The latch mechanism includes a magnetassembly 280 provided on second support post 270 and latch arm 282,including latch finger 283, mounted on actuator arm 240. Magnet assembly280 has a slot 284 and contains the magnetic field provided by a magnet(not shown) so that the magnetic field affects latch finger 283 onlywhen latch finger 283 enters slot 284.

A resilient element 285 provided in slot 284 of magnet assembly 288functions as the inside diameter crash stop. A sleeve 288 provided onfirst support posts 268, combined with tab 290 on actuator arm 240function as the outside diameter crash stop.

Table 3 specifies certain performance characteristics of disk drive 200.

TABLE 3 Seek Times Track to Track 8 msec Average sub-19 msec Maximum 35msec Average Latency 8.8 msec Rotation Speed (±.1%) 3399 RPM ControllerOverhead 1 msec Data Transfer rate To/From Media 1/5 MByte/sec DataTrasfer Rate To/From Buffer 4.0 MByte/sec Interleave 1-to-1 Buffer size64 K byte

All seek times are determined for nominal d.c. input voltages. Averageseek times are determined by dividing the total time required to seekbetween all possible ordered pair of track addresses by the total numberof ordered pairs.

TABLE 4 Temperature Operating 5° to 55° Non-operating −40° C. to 60° C.Thermal Gradient 20° C. per hour maximum Humidity Operating 8% to 80%non-condensing Non-operating 8% to 80% non-condensing Maximum Wet Bulb26° C. Altitude (relative to sea level) Operating −200 to 10,000 feetNon-operating (max.) 40,000 feet

Table 5 specifies shock and vibration tolerances for disk drive 200.Shock is measured utilizing a ½ sine pulse, having a 11 msec duration,and vibration is measured utilizing a swept sine wave varying at 1octave per minute.

TABLE 5 Non-operating shock 75 G's Non-operating vibration 5-52 Hz0.020″ (double amplitude) 63-500 Hz 4 G's (peak) Operating shock 5 G's(without non-recoverable errors) Operating vibration 5-27 Hz .025″(double amplitude) 28-500 Hz .5 G's (peak) (without non-recoverableerrors)

Third Embodiment

A disk drive 300 in accordance with the third embodiment of the presentinvention will be described with reference to FIGS. 13-24.

As shown in FIGS. 13-20, the construction of disk drive 300 includes abase 312 and a cover 314, both generally formed of aluminum. Gasket 316provides a sealed, controlled environment substantially isolated fromambient atmospheric pressures between base 312 and cover 314. As will bediscussed in further detail below, a unique, elastomeric and metalgasket provides improved sealing of the disk drive in accordance withthe third embodiment. First and second disks 320, 321 are supported onbase 312 and rotated by spin motor 322. Motor 322 is mounted in a well323 in base 312, thereby allowing lower disk 321 to be as close aspossible to the top surface of base 312.

Basket 316 is formed to have a unique elastomeric and metal structurewhich provides improved sealing characteristics for disk drive 300 andease of assembly. Generally, hermetically sealed disk drives utilizegaskets formed entirely of an elastomeric material. As shown in FIGS. 13and 19, gasket 38 includes a metal layer 317 sandwiched between twoelastomeric layers 318 ₁, and 318 ₂. In one embodiment, layer 317 isformed of stainless steel and layers 318 ₁, and 318 ₂ are formed ofburtyl rubber. The structure of gasket 316 provides easier assembly inthe manufacture of drive 300 since the stiffness provided by the metallayer allows easier seating of the gasket structure on the base platethan drives using a purely elastomeric gasket. Gasket 316 furtherprovides a seal for the hermetically sealed, controlled environmentbetween cover 314 and base 312. In this regard, gasket 316 has a lateralstrength superior to that of purely elastomeric gaskets. The additionalstiffness, yielded through the use of a high modulus material, such asburtyl rubber, in conjunction with the stainless steel sandwiched layer,improves the drive's resistance to a phenomenon known as “blow out”,which can cause a conventional elastomeric gasket of a hermeticallysealed drive to deform with changes in external pressure relative to thepressure within hermetically sealed environment.

An actuator assembly 324 positions heads 326 a-d with respect to disks320 and 321; heads 326 a and 326 b read information from and writeinformation to respective, opposed surfaces of disk 320, and heads 326 cand 326 d read information from and write information to respective,opposed surfaces of disk 321. Disks 320, 321 may comprise platedmagnetic disks with an intensity of 1400 Oe. Table 6 below specifiescertain characteristics of disks 320 and 321 and heads 326 a-d. Heads326 a-326 d may comprise thin film, air bearing heads capable ofoperating at a minimum flying height of 4.3 micro-inch, with a gap widthof approximately 7.5 micron, a gap length of approximately 0.4 micron,with a head gram load of approximately 5 grams.

TABLE 6 Number of Disks 2 Number of Data Surfaces 4 Number of DataCylinders 2124 cylinders (Tracks per surface) Sectors per Track 50physical 49 accessible Bytes per Sector 668 bytes Data Bytes per Sector512 bytes Data Capacity per Data 53.3 Mbytes Surface (formatted) TotalData Capacity (formatted) 213.2 Mbytes Disk Diameter 95 millimeters 3.74inches Data Track Band Width 0.84 inches Track Density 2496 tracks/inchBit Density (max.) 30,452 fci

Controller 327, including printed circuit board 328 and the circuitrymounted thereon provides control signals to spin motor 322 and actuatorassembly 324, and provides data signals to and receives data signalsfrom heads 326 a-d, actuator assembly 324 and spindle motor 322. Header330 provides all electrical connections between controller 327 and theenvironment between base 312 and cover 314. Header 330 comprisesconductive pins 331 embedded in a plastic header 335 which is thenpotted in base 212. Bracket 332 supports a flex circuit 333, including areverse flex circuit loop 334, and connector 336 which provideselectrical interconnections between flex circuit 333 and pins 331.

Controller 327 may incorporate the system described in the aboveco-pending application entitled MULTIPLE MICRO CONTROLLER HARD DISKARCHITECTURE. The third embodiment of the present invention provides asubstantial increase in storage capacity within the same physical formfactor as the drives of the first and second embodiments byincorporating several different factors. Specifically, the read/writeheads used in the present invention, while being of the conventionalair-bearing design, utilize a so-called 70% slider, wherein thedimensions of the head and slider have been reduced by approximately 30%from the sliders utilized in the first and second embodiments of thedisk drive. In addition, the head gap width has been reduced toapproximately 7.5 micron, with a gap length of 0.4 micron. In addition,with an increase in the intensity of the storage media to a 1400Oe-plated disk, and an increase in track density to 2496 tracks perinch, the aforementioned controller architecture allows for an increasein the storage capacity of the disk drive to up to about 213 MBytes,using 49 user sectors and providing a data rate of 20 MBytes/second.

Printed circuit board 328 is mounted to base 312 by mounting screws (notshown), and an insulating sheet (not shown, similar to sheet 255) may beprovided between printed circuit board 328 and base 312 to prevent shortcircuiting of the solder points appearing on the back side 328 b ofprinted circuit board 328 which faces base 312. Printed circuit board328 has and opening 353, and well 323 protrudes through opening 353.

The disk drive of the third embodiment has a structure, which is similarto disk drive 200 of the second embodiment 60, that enables two (2)disks, 320 and 321, to lie in parallel planes within a one inch height,three and one-half inch form factor disk drive. In the first embodimentof the present invention the sloped profile of base 12 allowed the useof a fully shrouded power connector 58. In the third embodiment, as inthe first embodiment, base 312 have first and second side rails 313 aand 313 b, and the mounting surface of base 312 is parallel to the planedefined by support points 315 a-g. The space below base 312 is the sameat both ends of drive 300; thus, in the third embodiment a slopedprofile is not utilized. As with the second embodiment of the disk driveof the present invention, the placement of motor 322 in well 323 allowstwo disks 320 and 321 to be provided in substantially parallel planes.

Printed circuit board 328 may include an interface connector, powerconnector, and test connector similar to that utilized in the secondembodiment of the drive of the present invention.

The specific structure, operation, and features of actuator assembly 324will be explained with reference to FIGS. 14-18 and 20. The function ofthe actuator assembly 324 is to position heads 326 with respect to thesurfaces of disks 320, 321 by pivoting actuator arm assembly 340, andmore specifically, to position the heads 326 over individual tracks ondisks 320, 321. Heads 326 are supported on actuator arm 340 by loadbeams 360. A bearing cartridge 362, which is fixed to the base plate 312at mounting region 312 a, is inserted in actuator arm 340 to allow arm340 to rotate about pivot point “A” (FIG. 20). Actuator arm 340 isattached to bearing cartridge 362 by a clip ring 363. As noted above,using clip ring 363 instead of epoxy allows the bearing cartridge 362 tobe tested prior to assembly and cleaned independently of the actuatorarm 340. Heads 326 may thus be positioned along an arcuate path at anyindividual data track between innermost data track 295 and outermostdata track 296 by the voice coil motor as described below.

The force utilized to pivot arm assembly 340 is provided by a so-calledvoice coil motor comprising coil 342 (provided on actuator arms 340-1,340-2), first and second magnets 346 a, 346 b, top plate 364, bottomplate 366, support post 368, and latch body 370. Actuator assembly 324provides a unique coil and magnet design which improves the efficiencyof the actuator by providing a relatively constant amount of torque onarm 340 throughout its rotational movement. Top and Bottom plates 364and 366, in conjunction with first support post 368 and latch body 370create returns for the magnetic fields provided by first and secondmagnets 346 a and 346 b. (The general operation of the voice coil motoris described above with respect to the first and second embodiments.) Itis important that there are no air gaps between support posts 368, latchbody 370 and either the top or bottom plate 364, 366; any air cap wouldcreate a discontinuity in the return, greatly reducing the strength ofthe magnetic field.

First and second magnets 346 a, 346 b are bipolar, each having a firstand second region 346 ₁, 346 ₂ with opposite poles attached to top plate364 (e.g., the south pole of first magnet 346 a and the north pole ofsecond magnet 346 b are attached to top plate 364) to provide first andsecond magnetic fields {right arrow over (B)}₁, {right arrow over (B)}₂,between respective ones of the first and second magnets 346 a, 346 b andbottom plate 366. First and second magnetic fields {right arrow over(B)}₁, {right arrow over (B)}₂ are encompassed in a closed magneticfield loops provided by top plate 364, bottom plate 366, support post368, and latch body 370.

Actuator coil 342 is positioned so that it carries a current in oppositedirections in first and second magnetic fields {right arrow over (B)}₁,{right arrow over (B)}₂. The strength of the magnetic field in thisregion between magnets 346 a, 346 b is directly related to the torquewhich the voice coil exerts on the actuator arm 340, and thus therotational velocity of actuator 340 and the seek times for the drive.

The force on a current carrying wire in a magnetic field is proportionalto the magnetic field intensity, and is expressed by the equation {rightarrow over (F)}={right arrow over (i)}dl×{right arrow over (B)}, where Fis the force, i is the current, l is the length of the wire, and B isthe magnetic field. Passing a current in opposite directions in actuatorcoil 342 provides respective forces {right arrow over (F)}₁ and {rightarrow over (F)}₂ (FIG. 17); these forces {right arrow over (F)}₁ and{right arrow over (F)}₂ pivot actuator arm 340 in opposite directionsabout and axis passing through the center of bearing assembly 362.

Actuator arm 340 may be fabricated of magnesium, including all of thecomponents attached thereto, is precisely balanced, i.e., equal amountsof weight are provided on either side of the pivot point so that thepositioning of heads 326 is less susceptible to linear shock andvibration.

Testing of the voice coil motors of conventional disk drives has shownthat the magnetic field strength at the peripheral portions of actuatormagnets is less than the magnetic field strength at the central portionof actuator magnet. Presumably, this is because the direction ofmagnetic flux between plates 364, 366 near the central portion ofmagnets 346 a, 346 b is essentially vertical, as shown in FIG. 16 bymagnetic field {right arrow over (B)}₁, and {right arrow over (B)}₂. Asone moves outward from the line of division between regions 346 ₁ and346 ₂ toward the periphery of the magnet (sides 347-1 and 347-2), thedirection of the magnetic flux tends to become non-perpendicular withrespect to the surface of magnets 346 a, 346 b. This has the effect ofreducing the torque exerted by the voice coil motor on the actuator arm340 when the arm is moving toward the innermost track 295 or outermosttrack 296. FIGS. 21, 22, and 23 show that the torque generated by thevoice coil motor in the first (FIG. 21) and second (FIGS. 22-23)embodiments of the present invention decreases as actuator arm 340positions heads 326 at inside diameter track 295 and outside diametertrack 296. FIG. 21 is a graph of the torque applied to actuator arm 40of the disk drive of the first embodiment of the present invention uponacceleration of arm 40 in response to a seek command from controller 28.As shown in FIG. 21, the loss recorded at the inside and outsidediameter position of heads 26 is approximately 6% for the drive tested.Experimental results on a number of similar drives a typical loss at theinside and outside diameters of approximately 10%.

FIGS. 22 and 23 are graphs showing the relationship between the torqueapplied on acceleration of the actuator arm 240 of the disk drive of thesecond embodiment of the present invention in relation to the positionof heads 226 at the inside and outside diameter tracks of disk 220. Asshown therein, the two drives tested show losses at the inside andoutside diameters of the disk of approximately 12% and 10% respectively.

To provide a greater efficiency for the actuator of the third embodimentof the present invention, coil 324 and magnets 346 a, 346 b have beendesigned to provide both a greater effective area of coil 324 in thepresence of magnetic field {right arrow over (B)}₁ and {right arrow over(B)}₂, and a greater magnetic field intensity at the peripheral edges ofthe magnets.

FIG. 20 details the relationship between coil 324 and actuator magnet346 b as such, top plate 364 has been removed. It should be generallyunderstood that the following principles, described in conjunction withmagnet 346 b, apply equally to magnet 346 a provided on top plate 364.In order to compensate for torque losses at the inner diameter and outdiameter, the surface area of magnet 346 b is appreciably increased withrespect to the actuator magnets shown in the first and secondembodiments of the present invention. Specifically, magnet 346 bincludes a greater surface area at the respective ends 347-1 and 347-2of the magnet, over which coil portions 324 ₁ and 324 ₂ are positionedwhen heads 326 are at inside diameter 295 or outside diameter 296 ofdisk 320. The curvature of magnet edge 348, positioned closest the axisof rotation of actuator body 340. The arcuate shape of magnet edge 348is such that it has a near tangential relationship with respect to edges324 ₃ and 324 ₄ of coil 324, and is defined to have constant radius “X”with respect to “B”, adjacent magnet 346 b. In one configuration, radius“X” is approximately 0.387 inch. Magnet 346 b also includes an outeredge 345, comprising first and second edges 345 ₁ and 345 ₂, meeting, atan angle, at the division of regions 346 ₁ and 346 ₂ of magnet 346 b. Aswill be noted from an examination of FIG. 12, only the linear, uncurvedportions of coil 242 overlie magnets 346 a and 246 b in the secondembodiment. In the third embodiment of the present invention, coil 324has been modified so that more coil area is provided over the majorsurface of magnet 346. Specifically, in the disk drive of the secondembodiment of the present invention, approximately 35% of the coil areais utilized; in the third embodiment, coil area utilization is increasedto approximately 43%. Thus, a greater amount of coil area is provided inmagnetic fields B₁ and B₂, therefore providing greater efficiency in thevoice coil motor of the third embodiment of the present invention andgreater torque on actuator arm 340. Specifically, it is estimated that,due to both the improvement in the shape of magnets 346 a. 346 b and theshape of coil 342, having a small curved area close to actuator pivotpoint “A”, the usable area of the coil is increased in this embodimentto approximately 43%. Further, because of the increased field strengthprovided by the greater surface area of magnet 346 b near magnet ends347-1 and 347-2, the drop off associated with the acceleration torque inthe first and second embodiments of the present invention is reduced. Asshown in FIG. 24, the acceleration torque has a greater “linearity” thanthe acceleration torque shown in FIGS. 21-23. That is, the torqueprofile of the voice coil motor of the third embodiment is nearly linearbetween the inner diameter and the outer diameter, exhibiting less of anarcuate shape than the profiles depicted in FIGS. 21-23. Magnetic fluxand torque loss associated with the positioning of the heads at theinner or outer diameters is markedly reduced, resulting in a total lossof torque of about 3% for the drive tested with respect to FIG. 24.

The actuator design of the third embodiment of the present inventionresults in an improvement of approximately 4.7% in access time.

Generally, the seek time specification for hard disk drives isdetermined in relation to the drive's minimal expected efficiency. Thatis, in conventional drives, the lowest actuator torque constant (K_(t))for a given drive between the innermost track and the outermost track ofthe disk is used to generate the expected seek profiles for the drive.Losses occurring primarily at the peripheral edges of actuator magnetscreate longer seek times. The benefits of the higher torque magnitudes,generated over the central areas of the magnet, is lost.

Actuator disk access is generally divided into three segments controlledby the control means: a full acceleration of the actuator toward thetrack; a controlled deceleration of the actuator to a point within aspecified area near the track (typically ¼ track width); and apositioning loop, for accurately locating the head over the desiredtrack, also known as “settling. The raw average access time is definedas comprising the acceleration and deceleration of the actuator. Theeffective improvement in average access time can be shown mathematicallyas follows. The raw average access time for a drive, such as that shownin FIGS. 13-20, is given by:$T = {\left\lbrack {1 + \frac{Va}{Vd}} \right\rbrack \sqrt{\frac{2\quad \theta \quad s}{Kt}}\frac{JR}{Va}}$

where

θ_(s)=the distance, in radians, of travel from start to finish for theactuator (typically ⅓ of a full stroke, 0.07 rad);

J=the polar inertia of a moving actuator (23.0×10⁻⁶ in-lbs²);

R=the resistance, in ohms, of the coil (25 Ω);

K_(t)=the motor torque constant (typically 0.7 in-lb/amp);

V_(a)=the voltage applied to accelerate the actuator (9.5 v); and

V_(d)=the voltage applied to decelerate the actuator (5 v). For purposesof clarity, the above equation neglects the effects of coil inductance,back EMF and assumes a controlled deceleration.

Given the above values, the total computed access time is 10.09 ms. Byimproving the torque constant, e.g., the “linearity” of the magneticfield over the full stroke of the actuator arm, and improvement inaccess time for the drive will follow, as shown in the followinganalysis.

By holding all variables except K_(t) constant, the torque equation issimplified to: $T = {K_{1}\sqrt{\frac{K_{2}}{K_{t}}}}$${{{where}\quad K_{1}} = {{1 + {\frac{Va}{Vd}\quad {and}\quad K_{2}}} = \frac{2\quad {\theta \quad}_{s}{JR}}{Va}}},\quad {{we}\quad {find}}$$\begin{matrix}{T = {K_{1}\sqrt{\frac{K_{2}}{K_{t}}}}} \\{= {K_{1}\sqrt{K_{2}}\left( \frac{1}{\sqrt{K_{t}}} \right)}}\end{matrix}$${{{If}\quad K} = {K_{1}\sqrt{K_{2}}}},\quad {then},\quad {T = {K\left( \frac{1}{\sqrt{K_{t}}} \right)}}$

If, then, the torque constant K_(t) is increased by a factor of 10% sothat $\begin{matrix}{T = {K\left( \frac{1}{\sqrt{1.1K_{t}}} \right)}} \\{= {K\left( \frac{1}{\sqrt{1.1\sqrt{K_{t}}}} \right)}} \\{= {{.953}{K\left( \frac{1}{\sqrt{K_{t}}} \right)}}}\end{matrix}$

Thus, for every 10% improvement in the torque constant, a 4.7%improvement in access time, T can be seen.

Hence, by increasing the total minimum torque constant by increasingsurface area of the voice coil magnet and the area of the coil in thefield generated by the voice coil magnets, the average seek times forthe drive can likewise be decreased.

Crash stops are provided to limit the pivoting movement of the actuatorarm 340 so that heads 326 travel only between selected inside andoutside diameters 295, 296 of disk 320. An outside diameter crash stopis provided by a sleeve 376 (FIGS. 16, 17, and 20) fitted on supportpost 368. When the pivoting motion of actuator arm 340 places heads 326at the outside diameter 296 of disk 320 portion 242 of actuator arm340-2 contacts outside diameter crash stop 376, thereby preventingfurther movement of the heads 326. An inside diameter crash stop isprovided by the portion of the latch mechanism and is described below.

A latch mechanism for locking actuator arm 340 will be described withreference to FIGS. 14-20.

The latch mechanism of the third embodiment of the disk drive of thepresent invention utilizes the force of the voice coil actuator magnets346 a and 346 b to provide the magnetic retentive force for the latchingactuator 340.

As can be seen in FIGS. 14-20, a capture pin 130 formed of magneticallypermeable material is provided in latch arm 340-1. Latch supportstructure 270 is designed so that the magnetic circuit formed byactuator magnets 346 a and 346 b provides a flux path through structure270. Voids 398-1 through 398-4 are formed in structure 270 to channelthe magnetic flux from magnets 346 a and 346 b to air gap 399.Specifically, air gap 399 has a width W of approximately 0.012 inches.Capture pin 130 is generally “T” -shaped, including portion 131extending through a bore in actuator latch arm 340-1 and secured theretoby a snap ring (not shown). The magnetic flux provided by magnets 346 aand 346 b and channeled through support structure 270 exhibits afringing effect when the flux encounters gap 399. When actuator 340 isdirected to position heads 326 over the landing zone at inner diameter295, capture pin 130 is drawn into abutment with tabs 398 a and 398 b ofstructure 270. As pin 130 engages tabs 398 a, 398 b, the magnetic fluxprovided by magnets 346 a and 346 b passes through pin 130, making pin270 part of the magnetic circuit formed by structure 270 and magnets 346a, 346 b.

The latching force provided by the latching mechanism is 50-60inchgrams. The amount of latching force may be adjusted by providing ashunt 375 (FIG. 16) across gap 399 to provide a flux path in parallelwith the flux fringing about gap 399. Generally, there is no need for anadditional latch magnet to provide the requisite magnetic latching andreleasing forces for the actuator. Actuator assembly 324 can generatesufficient force to release actuator arm 340 from the latched position.The strength of the latching force is sufficient to retain the actuatorin a captured position under non-operating shocks of up to 75 G's.

Table 8 specifies certain performance characteristics of disk drive 300.

TABLE 8 Seek Times Track to Track 3 msec Average 12 msec Maximum 25 msecRotation Speed (±.1%) 4491 RPM Data Transfer Rate To/From Media 20MByte/sec Interleave 1-to-1

Table 9 specifies certain environmental characteristics of disk drive300.

TABLE 9 Temperature Operating 5° C. to 55° C. Non-operating −40° C. to60° C. Thermal Gradient 20° C. per hour maximum Humidity Operating 8% to80% non-condensing Non-operating 8% to 80% non-condensing Maximum WetBulb 26° C. Altitude (relative to sea level) Operating −200 to 10,000feet Non-operating (max.) 40,000 feet

Table 10 specifies shock and vibration tolerances for disk drive 200.Shock is measured utilizing a ½ sine pulse, having a 11 msec duration,and vibration is measured utilizing a swept sine wave varying at 1octave per minute.

TABLE 10 Non-operating shock 75 G's Non-operating vibration 63-500 Hz 4G's (peak) Operating shock 5 G's (without non-recoverable errors)Operating vibration .5 G's (peak) (without non-recoverable errors)

The many features and advantages of the disk drive of the presentinvention will be apparent to those skilled in the art from theDescription of the Preferred Embodiments. For example, those skilled inthe art will appreciate that the structure of the disk drive of thepresent invention as described herein can be scaled for use with diskdrives having disks with smaller and larger than 3½ inches. Thus, thefollowing claims are intended to cover all modifications and equivalentsfalling within the scope of the invention.

What is claimed is:
 1. A disc drive apparatus comprising: a base platesupporting a head disc assembly; a cover over the head disc assemblyfastened to the base plate to provide a controlled environment for thehead disc assembly between the base plate and cover; and a printedcircuit board adjacent to an underside of the base plate, the base platehaving parallel longitudinal side walls and end walls forming a spaceunder the base plate for receiving components mounted on the printedcircuit board, wherein one of the end walls has an opening therethroughfacing a power connector and a signal connector on the printed circuitboard and the other of the end walls has an opening therethrough alignedwith another connector on the printed circuit board facing outward in aparallel.and opposite direction to the power and signal connectors. 2.The disc drive apparatus according to claim 1, wherein the anotherconnector further includes a plurality of pins for receiving a matingsocket connector for transferring electrical signals to and from theprinted circuit board.
 3. A disc drive apparatus comprising: a baseplate supporting a head disc assembly from an upper surface of the baseplate; and a printed circuit board beneath the head disc assemblyfastened to an underside of the base plate forming a space under thebase plate for receiving components mounted on the printed circuitboard, the printed circuit board having a first and a second end, thefirst end having a power connector and a signal connector operablysupported on the printed circuit board and facing away from the circuitboard and the second end opposite the first end supporting anotherconnector for transferring electrical signals to and from the printedcircuit board, the another connector facing outward from the printedcircuit board in a parallel direction opposite to the power and signalconnectors.
 4. A disc drive apparatus comprising: a base platesupporting a head disc assembly from an upper surface of the base plate;and a printed circuit board fastened to an underside of the base plateforming a space under the base plate for receiving components mounted onthe printed circuit board, the printed circuit board having a first anda second end, the first end having a power connector and a signalconnector operably supported on the printed circuit board and facingaway from the circuit board and the second end opposite the first endsupporting another connector for transferring electrical signals to andfrom the printed circuit board, the another connector facing outwardfrom the printed circuit board in a parallel direction opposite to thepower and signal connectors wherein the base plate has side walls andopposite end walls together enclosing the printed circuit boardtherebetween, one of the end walls having an opening in registry withthe power connector and signal connector, the other of the end wallshaving another opening aligned with the another connector.